A spectrum resource is a basis of wireless communications. Different spectrum resources are allocated to and used by different communications systems or communications devices, and different communications systems use respective spectrum resources according to respective stipulated rules. Moreover, in the prior art, a spectrum resource that can be used by different communications systems further exists, for example, an unlicensed (unlicensed) spectrum resource.
According to a recently released international spectrum white paper of the Federal Communications Commission (FCC) in USA, unlicensed spectrum resources are currently more than licensed spectrum resources, and the unlicensed spectrum resources are mainly applied to Wireless Fidelity (WiFi). WiFi has disadvantages in aspects such as mobility, security, quality of service (QoS), and simultaneous processing on multi-user scheduling. Therefore, it may be considered that unlicensed spectrums are applied to wireless communications systems. In this way, not only the unlicensed spectrum resources may be effectively used, but also more effective wireless access may be provided, to satisfy ever-growing mobile broadband service requirements. Unlicensed spectrums used by wireless communications systems and operators are not constrained, and therefore, a case in which multiple operators of multiple communications systems intend to occupy a same spectrum resource exists on the unlicensed spectrums.
In some regions, for use of unlicensed spectrums by wireless communications systems, regulations and rules that need to be followed are regulated. For example, in ETSI EN 301 893 released by the European Telecommunications Standards Institute (ETSI), rules such as Listen-Before-Talk (LBT) and a channel bandwidth occupation requirement are regulated for use of unlicensed spectrums. According to a regulation of the ETSI EN 301 893, when performing communication by using an unlicensed spectrum a wireless communications system needs to follow the LBT rule, that is, before using a channel on an unlicensed spectrum, a node first listens to whether the channel is idle, and if the channel is idle, the node may use the channel on the unlicensed spectrum. However, a time for which the channel is occupied is limited, and after the time for which the channel is occupied reaches a maximum limitation, the channel needs to be released for a period of time. According to the regulation of the ETSI EN 301 893, a longest time for which a wireless communications system occupies a channel on an unlicensed spectrum once is 13 ms. Before the channel needs to be occupied next time, the node needs to listen again to whether the channel is idle.
By using Long Term Evolution (LTE) as an example, according to the regulation of the ETSI EN 301 893, before using a channel on an unlicensed spectrum, user equipment (UE) of an LTE system needs to listen to whether the channel is idle. If the channel is idle, the channel is used to transmit uplink data. However, a system resource is allocated in the LTE system in a dynamic shared resource scheduling manner. For uplink data transmission of the UE, an occupied wireless communications resource, a data transmission coding scheme and the like are all indicated by an Evolved NodeB (eNodeB) by using control signaling.
Specifically, in LTE, regardless of an FDD system or a time division duplex (TDD,) system, a relationship between any uplink data transmission and corresponding uplink data scheduling is predefined. For a frequency division duplex (FDD) system, when UE detects, in a subframe (subframe) #n, a PDCCH/EPDCCH that is sent by an eNodeB and that is used to schedule the UE to transmit uplink data, the UE performs uplink data transmission in a subframe #n+4 according to indications of the physical downlink control channel (PDCCH)/enhanced physical downlink control channel (EPDCCH) and a physical hybrid automatic repeat request indicator channel (PHICH). For a TDD system, when UE detects, in a subframe #n, a PDCCH/EPDCCH that is sent by an eNodeB and that is used to schedule the UE to transmit uplink data, the UE performs uplink data transmission in a subframe #n+k according to indications of the PDCCH/EPDCCH and a PHICH, where a value of k is related to a TDD uplink-downlink allocation configuration and n, as shown in Table 1:
TABLE 1value of k in a TD-LTE 0-6 timeslot allocation mannerTDD timeslot Subframe numberallocation01234567890464616464244344444454677775
In this way, when an unlicensed spectrum is used as an operating spectrum of an LTE system, using an FDD system as an example, it is assumed that in the FDD system, UE receives, in a subframe #n−4 and by using a PDCCH, uplink data scheduling information sent by an eNodeB, and needs to send a PUSCH to the eNodeB in a subframe #n, while on an eNodeB side, whether the UE may obtain, by listening to a channel on the unlicensed spectrum, an opportunity for sending uplink data in the subframe #n cannot be “foreseen” by the eNodeB in the Subframe #n−4.
If the eNodeB performs uplink data scheduling on the channel on the unlicensed spectrum on the UE (for example, in the Subframe #n−4 in the FDD system), and when preparing to send uplink data in the subframe #n according to a conventional time sequence relationship between scheduling and transmission of uplink data of the LTE system, the UE detects that a resource of the channel on the unlicensed spectrum is occupied, and cannot send uplink data on the channel according to an indication of the eNodeB, while the eNodeB does not know whether the channel on the unlicensed spectrum detected on a UE side is occupied, the eNodeB misunderstands that the UE already sends uplink data according to a scheduling indication, and receives and demodulates the uplink data in the subframe #n. Because the UE cannot acquire the opportunity for sending uplink data in the subframe #n, and the eNodeB determines that data transmission fails, and misunderstands that the data transmission fails due to poor channel quality, the eNodeB saves or merges a receiving and demodulation result into a soft storage area, to obtain an erroneous data transmission result, reducing transmission efficiency of a wireless communications system.
To resolve the foregoing problem, in the prior art, when detecting that a channel on an unlicensed spectrum is idle, UE occupies a resource of the channel in advance, and notifies an eNodeB of information that the channel on the unlicensed spectrum is available. After receiving a notification that the channel on the unlicensed spectrum is available, the eNodeB schedules the UE to perform uplink data transmission. For example, if the UE confirms in a subframe #n that uplink data may be sent on the channel on the unlicensed spectrum, the UE sends random data on the channel starting from the subframe #n, so as to ensure that the UE may still use the channel in a subframe #n+x, and the UE notifies the eNodeB of a message that the UE may occupy the channel. In this way, after receiving a notification of the UE, the eNodeB may schedule the UE to transmit uplink data in the subframe #n+x of the channel on the unlicensed spectrum.
However, if the UE continuously sends random data on the channel on the unlicensed spectrum from the subframe #n to the subframe #n+x, on one hand, power of the UE is impaired, and on the other hand, because meaningless data is transmitted on the channel on the unlicensed spectrum, a wireless communications resource is wasted.